@mark-coniglio hi Mark. At this time I am not aware of any regression with the mentions plugin, which would usually point to some sort of configuration error.
Do you see any errors on the client side, in the browser dev tools?
1 or 2 reporting the same issue, Submit button goes grey when they click submit, then nothing happens. They're not very tech savvy, so asking them to look in their console would probably involve a screwdriver and a PS3. Anything you guys have suffered with before? Using latest Chrome & IE.
Should add, fine for me on all browsers. :s